I tested them on ACC's about 6 months ago. With a good offset, I found they did very well with fixed, vented blade heads 100 gns and less, with cutting diameters 1 1/8" and less. With bigger, heavier heads, accuracy and consistency went to pot. Obviously, they'd be fine for mechs too.

There's nothing special about them. They're just very thick and very stiff. Nothing flappy about these vanes.

But I'll stick with feathers.